I have a 98 ml320 with almost 130k. It has been changed with regular oil 20W-50 every 4-5k regularly. In the last year or so, it consumed abut a quart in between oil changes. I read the post on switching to synthetic. So I used 15W45 Mobil one. With this new synthetic, the engine consume a quart immediately after about 1,000 miles. I filled it up with more synthetic oil and after another 1,000 miles, another quart is consumed. The engine runs fine. There is no missing. I don't think there is fouling of the plugs. This worries me. Do I have worned rings or valves? Planning to change back to regular dino 20W-50 and back to regular 4k changes. If consumption is still high, I will probably have to trade it in for another MBZ(?) or other. I was hoping to get 200k on this truck. Any thoughts or experience out there?

John